Internal-combustion percussion tool



Dec. 23, I947. c. s. WEYANDT I 2.433.007

INTERNAL- COMBUST I 01 PERCUS S ION TOOL Filed July 30, 1945 4 Sheets-Sheet 1 3nnentor CAR]. 5. WEYANDT (Ittorneg Dec. 23, 1947. c. s. WEYANDT INTERNALCOMBUSTION PERCUSSION TOOL I Filed July 30, 1943 4 Sheets-Shegt 2 3nncmor CARL S. WEVAMZT c. s. wzmunw HZIEWL-COIBUSTIUN PERCUSSION Filed July 30 1943 4 Sheets-Sheet 5 I 3nu cntor CAN. SJ'EMMT attorney Dec. 23, 1947-- v c; s. WEYANDT I IITERNAL-GDHBUSTION PERCUSSION TOOL 4 1 MW 3 it w Filed July 30,, 1943 A. u 5 a r PatentedDec. 23,1947

UNITED STATES PATENT orrlce INTERNAL-COMBUSTION PERCUSSION TOOL Carl S. Weyandt, Indiana, Pa. Application July so, 1943, Serial No. 496,709

16 Claims.

The present invention. relates to percussion tools operated by internal combustion of a fuel, and relates particularly to such tools employing a free working piston.

Heretofore it has been proposed to provide a percussion tool of this type having a captive piston which controls the combustion of and a free differential piston which is impacted against the tool by the combustion of the fuel .and is returned by the pressure of the exhaust gases, the return stroke being cushioned by a gas cushion. However, I have found that in operation-the reciprocation of the differential or working piston is irregular so that the blows delivered thereby are not uniform, nor. is the maximum power of the apparatus developed. Furthermore, it becomes diflicult to supply oil to the walls of the differential cylinder, so that the life of the apparatus is considerably shortened due to the great wear on the working piston and its cylinder walls.

It is an object of thisinvention to improve the operation of percussion tools of this type to provide a more uniform piston.

Another object is to increase the efficiency of the apparatus by increasing the power of the working piston.

operation of the working Another object of this invention is to provide a device of this kind in which the action of the working piston may be controlled independently of the idling piston. r v

Still another object is the provision of an apparatus of this type which may be operated'in vertical or horizontal position. A further object of this invention is to provide a device of this kind in which the timing action of the working piston may be self-controlled- According to one feature of the present invention, I provide in an internal combustion percussion tool having an idling piston and a differential working piston driven in one direction bycombustion of the fuel and returned by the pressure of exhaust gas, a cushioning means for the return stroke of the working piston which enables the working piston to return to substantially the same position at the commencement of each working stroke. This is accomplished, for example, by. the provision of a buffer of resilient solid material for limiting the return stroke of the working piston. Suitable resilient solid 'materials for this purpose are the so called synthetic rubbers, particularly those which are oil resistant, and which are diene, its homologues and substitution products,

Neoprene the fuel polymers of butaor copolymers thereof with acrylonitrile or other unsaturated compounds having an unsaturated linkage adjacent the end carbon atom. Examples of such materials commercially available are which is a polymer of chlorine substituted butadiene, namely chloro-2-butadiene- 1,3, and Cogene and Ameripol which I believe to be copolymers of butadiene with acrylo- ,nitrile in various proportions. not disintegrate under repeated impacts and are resistant to gasoline, oil and grease and heat. The buffer may be applied to such apparatus in which the exhaust return port in the combustion chamber is controlled either by the working piston or by the idling piston.

The timing of the. idling piston preferably is controlled by imposing a load thereon, and in the preferred embodiment this load is imposed by a centrifugal governor or brake which controls the speed of rotation of the crankshaft and thus controls the frequency of reciprocation of the idling piston.

By providing a special carburetor the apparatus may be used in practically a horizontal position. The special carburetor has the fuel outlet to the motor at the middle of the fuel bowl the axis of which is inclined to the axis of the motor and adjacentthe bottom so that the outlet always will be under the fuel level, and the fuel level is controlled by an annular type float so that it will be effective inall positions of the apparatus.

For a detailed description of the invention, reference is had to the following specification taken in connection with the accompanying drawing, wherein preferred embodiments of the invention I are shown by way ofexample, and wherein:

Figure 1 is a side view partly in vertical section and with parts broken away of a preferred em-- 0 bodiment of the invention,

Figure 2 is a side view taken in the direction of the arrow II in Figure 1, I

Figure 3 is a vertical section of the lower portion of the embodiment shown in Figure 1,

Figure 4 is a vertical sectional view of the carburetor, a

. Figure 5 is a vertical sectional view of a portion of a modification,

Figure 6 is a side elevation of a detail of the modification shown in Figure 5, v

Figure '7 is a bottom view of a detail,

Figure 8 is a vertical sectional view of a further modification,

Figure 9 is a top view of a detail,

Such materials do haust pipe side.

Figure is a vertical sectional view of a detail of the carburetor,

Figure 11 shows the choke valve operating handle, v

Figure 12 shows the mounting of the fioat lever,

Figure 13 shows 'a modified exhaust conduit, and

Figure 14 shows a detail of thefuel tank cap.

Referring to the drawing, Figure 1, there is shown a casting or motor block I of cast iron having heat radiating fins and having a bore 2 therein which provides a chamber or cylinder n which the piston 3, which is called an idling piston, is adapted to reciprocate. This piston is suitably connected, as by a connecting rod 4, with the crankshaft 5 joumalled in suitable ball bearings in the crankcase 6 bolted to housing I, and the crankshaft bearings are sealed, by suitable seals 8. The lower part of the housing accommodates a working piston 9 to be later described in detail, and the middle part i of as a combustion chamber.

Gasoline, containing oil for lubrication of the moving parts of the apparatus, is contained in a tank In (Fig. 2) suitably attached to the apparatus, and is mixed'with air in a carburetor Ii of suitable construction to be later described in detail. On the down stroke of piston 3 a'mixture of air and gasoline is drawn inc the piston chamber 2 through the divided intake port l2 which is uncovered by the piston skirt near the lower end of its stroke, and when the piston moves upwardly it compresses the fuel charge in the crankcase 6. As the piston continues to move upwardly it first uncovers the exhaust port l5 and then uncovers the intake port I4, thus forcing the combustible charge from thecrankcase through the conduit "5 and port l4 into the combustion chamber 1, the piston head being suitably baffled to. prevent the incoming fuel being discharged through the exhaust port. The crank returns the piston to compress the charge in combustion chamber 7, which is ignited by the spark plug I3, the electric current for operating the spark plug being obtained from a combination magneto and flywheel II on the crankshaft 5. A fan l8 on the crankshaft draws air through a suitable screen I!) and forces a draft of cooling air against the fins on the motor block, a shroud or housing 20 being provided to defiect the air downward and against the fins. An external line 20a is connected to the exhaust port-15 to deflect the exhaust downward. The shroud or housing is located to guide the cooling air substantially horizontally between the fins on the motor block, the air entering the housing on the spark plug side and leaving on the ex- An opening covered by a removable plate 20b ma be provided to allow access to the spark plug.

The bore 2| in the casing below the combustion chamber constitutes a prolongation of bore 2 and portion 26 preferably has twice the area of end 22 which may be of any size desired, and need not be, but preferably is, the same diameter as piston 3. Suitable rings and an oil groove 21 may be provided to form a sealing contact between the piston 9 and the walls of chambers 2| and 24. I prefer to provide a. working clearance between the housing serves 4 the piston and its chamber of about 0.005 inch to prevent seizing at the elevated temperature created in operation. Piston 9 has an extension 28 which passes with a close fit through a-guide bushing 29 of tool steel or other suitable material and is adapted to strike the end of a tool 3| of any kind, such as a drill or tamper bar, loosely received in the tool holder '32 and longitudinally movable therein. Guide bushing 29 is clamped between the block I and the flanged tool holder or sleeve 32 in any suitable manner, and a dowel may be provided for proper positioning thereof. The working piston 9 preferably is guided in its reciprocation by the stem or extension 28 working in guide bushing 29 and the smaller end 22 workingin bore 2|, and the enlarged portion 26 need not have an accurately controlled clearance with the cylinder wall 24 as it carries a sealing ring of known construction which extends beyond the surface thereof and contacts the bore.

A buffer ring 33 is located in a recess 34 at the upper end of cylinder 24 which has one or more openings 35 to provide a relatively free passage of air to and from the upper end 24a of cylinder 24 to allow the piston to contact the buffer and to assist in cooling the buffer. Buffer 33 preferably is composed of a synthetic rubber material, the materials known as Cogene" or Ameripol and having a durometer hardness of about 50 to having been found especially suitable. I,prefer material having a durometer hardness of about 65. These materials are believed to be polymerized compounds of butadiene with acrylonitrile and are sold under the above trade names by Goodyear Rubber Co. and Goodrich Tire and Rubber Company, respectively.

The guide bushing 29 is recessed at 36 to cooperate with a slot 31 and two slots 38 located in the end of member 28 which merge with the reduced end 39 thereof in chamber 4i, and suitable holes 40' in holder 32 allow escape of gas therefrom to the atmosphere. Slot 31 is of such length that when the working piston is at the upper limit of its stroke its upper end is uncovered by the recess 36 so that slot 31 and both slots 38 in this position register with the bottom of recess 36 and thus provides a relatively free escape for gas from the chamber 24b to the chamber 4! at the top of tool 3!. On the downward stroke slot 31 first moves out of registry that all slots are disconnected from chamber 24b when the extension 28 impacts the tool. Should the tool be raised from the work during operation there is thus provided a gas cushion trapped in the lower end of chamber 24b to prevent the piston impacting the housing.

The tool 3| has flange 40 and a retainer 4i is provided to prevent accidental removal of the tool If it is desired to move or operative position by means of the handle 43.

A bore 45 in the block I below the combustion chamber 1 opens into the cylinder 2! and has its outer end closed by a screw 46 which may be removed to allow cleaning of the bore. The location of bore 45 preferably is such that. in the normal impacting position of piston 9 on the down stroke it is uncovered by the smaller end 22, and when the piston 9 is at its upper limit terminating in a valve seat leakage of gas.

is preferred as its movement between opened and 30 1 reached by the working piston 9. A control valve housing 43 with suitable cooling fins thereon is e suitably bolted registering with bore to the block and has a passage 48 41 and a vertical bore 5| 52 with a valve opening 53 therethrough. A horizontal bore 54 connects at one end with bore 5| and registers with a bore 55 which thus joins bores 45 and 54. A valve piston 56 in bore 5| has tapered valve end 51 adapted to seat on seat 52 in thelowermost position of the valve piston. A rod 58 connects with the valve piston 15 and extends from the valve housing 48 through a packing washer 59, packing 60 and nut 5|, and a plug 62 of resilient heat and oil' resisting resilient material seals the upper end of bore 5|.

Plug 52 preferably is made of synthetic rubber 2o material, such as polymerized butadiene or, a copolymer with acrylonitrile. When piston valve 56 is raised sufficiently to bring plug 52' against washer 59 the tapered end 51 uncovers bore 54 thus providing a. passageway through bores '41, 49', valve orifice 53 and bores 5|, 54,55 and 45 into chamberll, and at the same time plug 52 seals the stem 58 to prevent This. control valve construction closed positions is a sliding one which breaks loose carbon depositsto allow the valve free to move.

The operation of the apparatus so far described now will be explained. The lowermost positions 35 of pistons 3 and 9 is approximately shown in Figure 1, and the uppermost position of piston 9 is indicated approximately bythe dot and dash line B. Piston 3 works in cylinder 2, and is forced upwardly by ignition of a combustible charge in A firing chamber 1. At the same time the explosion of the fuel charge forces piston 9 downwardly until extension 23 strikes the end of tool 3|, the slots 31 and 38 in the extension 28 allowing the air or gas in-chambe'r 24b to escape rapidly at 45 the initial part of this movement until slots 31 and 38 respectively cease to register with recess 36 near the end of this movement just prior to impact with the'tool. 'Assuming valve piston 55 is in its uppermost is uncovered by piston 9 on its downward movement, which occurs after the explosion takes place and after slots 31 and 38 are out of registry with recess 36, the high pressure exhaust gas is conducted through passages 45, orifice 53 and passages 49 and 41 to the lower chamber 24b and the gas pressure returns the working piston 9 to its upper position against buffer 33 and thus causes the piston to close against port 45 to trap her 241). Upward movement of piston 9 brings grooves 38 into registry with the recess 36 near the lower end of its stroke, and thus allows the exhaust gas in chamber 24b to bleed out through grooves '38, chamber 4|, and ports 42. groove 31 registers with depression 36, thus decreasing the pressure in chamber 24b.

The exhaust port I is first uncovered by the head of piston 3 and thenthe intake port 14 is uncovered so that forced into the chamber 2 through passage. IS. The crankshaft and flywheel return the piston 3 to compress the fuel charge, but because ofthe larger area of piston 2-5 compared-with the end 22, and notwithstanding the slow bleed 7 and at the other from chamber 241) position when the port 55, 54, bore 5|, 5

the exhaust gas in cham- Finally afresh explosive charge is 7 through groove 31. the pressure in chamber 24%- remains suflicient to hold the piston I at approximately its uppermost position against buffer 33 until the next explosion, which preferably occurs when the crank and piston 3 are about 40 before the dead center position. The buffer 33 is provided to cushion the impact of piston 22 at the upper end of its stroke, and the openings 35 permit relatively free entrance and escape of air to the chamber 240 above piston 26. I prefer to have port 45 controlled by the working piston 9, the weight of which is experimentally determined idling operation of the working piston 9 is thu obtained and the working piston is each time uniformly returned and held in its uppermost position in readiness for the next explosion, the number of strokes of'the working piston being synchronized with those of the idling piston.

The power of the apparatus is also increased by advancing the ignition so as to cause it to occur about 10 to about 45 or 50 before dead center. In this way the working piston and the idling piston are moving in the same direction so that a greater proportion of the explosion force is applied to the working piston. Further more by having the exhaust gas passage for returning the working piston controlled by the working piston and advancing ignition to about 35 to 40 before is transmitted to the piston return chamber 24b than if this passagewere controlled by the idling piston. This is because the port 45 is uncovered sooner and exposes a higher pressure than if the idling piston 3 passed through dead center and then uncovered this port. This increases the power of the apparatus, or weight apparatus can be made by having a lower ratio between the area of thetop surface of the smaller end 22 of the working piston and the effective area, of the lower surface of the enlarged portion 25. Thus, I may use a ratio of about 1 to 1.3 for a light weight apparatus, and a ratio of 11:0 2 for heavier more powerful apparatus, although the preferred ratio is about 1 to 1.5.

When actually working, the desired synchronism may not be obtained under all conditions, due to the reactive influence of the tool upon the working piston, but the bufier 33 to a large extent compensates for such variations. The buffer provides a more uniform action than an air cushion, and by allowing the working piston to assume a higher position than is possible by an air cushion, a greatercompression ratio of the fuel is obtained with resulting increase in power of the apparatus. Also I am abl to lubricate the walls of the differential cylinder by the 'oil dissolved in the fuel. The failure to provide adequate lubrication of the working piston in prior devices, I believe, is due to the scavenging action of the combustion which burns th oil off the cylinder wall, and is overcome by the use of a solidresilient buffer by allowing the piston to rise further and thus protect the lubricant on the cylinder wall. An air cushion tends to hold the working piston away from its uppermost position, and furthermore, air leakage will vary the upper position of the Working piston. Another possible explanation is that the pressure of the air cushion'resists the downward flow of oil on the cylinder wall. Whatever may be the explanation, I find that by substantially eliminating the air cushion for the return stroke of. the workingpiston and providing a buffer of 5 solid compressible material, I obtain an imfor best operation, as a uniform dead center, a higher pressure if desired, a lighter -98 and a passage 35 provement in the operation and lubrication of 7 the apparatus.

I prefer to use a butter of "Ameripol" for this purpose, but other synthetic or artificial rubber materials have been found to have an excellent durability under impact for this P pose and provide substantially noiseless bufllng action. The compression of the gas in chamber 24b below the piston 9, by reason of grooves 21 and 38 moving out of registration with recess 38, provide a cushioning action to cushion the strok of the working piston when the tool is raised from the work.

In the modification shown in Figures to 7 wherein like parts are correspondingly numbered, the lower portion 65 of the casing for housing the working piston is separate from the upper part I and is suitably secured thereto to enable drilling-the various passages required. A valve block 66 has a threaded boss 67 threaded into a bore 68 in the lower casing 65 and passage 58 communicates with a passage 69 therein. The valve block has threaded bores 1| and I2 at its ends and a connecting portion or chamber 13 to provideavalve seat 14.

The working piston 9 is made hollow and is closed at its upper end by a plug 22a threaded against a shoulder 22!) and welded at 220. In the valve block 66a valve I5 of the poppet type is seated on the seat 14 and has astem 16 extending through the bushing I7. the opposite bore 12 being closed by a, cap screw I8. An L-shaped passage 19 in the threaded boss 81 leads to annular groove 80 and. connects chamber 13 with the longitudinal passage 8| which connects by port 82 with the lower portion 24b of chamber 24. A threaded plug 83 closes the end of passage 8| and may be removed to allow the cleaning of the passage.

A bracket '85 extends from adjacent the upper' end of the motor block I and carries a guide bush- 86 through which extends the valve stem 16 the sprin abutting the bushing TI.

is secured at the upper end of chamber 24a in any suitable manner as by countersunk screws allows free entrance and escape of air from this chamber.

In operation passage 58 is closed from passage 82 by valve 15 held closed by spring 95 and the pressure of gas on the valve, and when an explosion in chamber 1 occurs the working piston 9 is driven downward to bring extension 28 into the cam 92 on crankshaft 5, or by adjusting the head 81, or by doing both, to cause the valveto open at the proper An annular buifer 88 ing IOI, and

time, and to close at the proper time. In this way through suitable lugs 98d on the block.

Referring to the modification shown in Figs. land 2, the fly wheel I! is encircled by a band IOI which has a friction brake lining I02 pressed therein. The fly wheel carries at its periphery a brake shoe I04, which preferably is of hardened steel and has turned over apertured lugs I06 by which it is pivoted to the periphery of the fly wheel by a pin I01 passing therethrough and through the lugs. The brake shoe carries an extension I88 which is engaged by one end of a spring I09, in a recess I I I in the fly wheel periphery, and the opposite end of the spring engages an adjustment screw |I2 threaded into the periphery of the fiy wheel and locked in position by a nut I I3.

In operation the brake shoe I04 is pivoted out- Wardly by centrifugal force operation and would tend to overheat. By adjusting the pressure of spring I09 against extension I08 by means of screw II2 the brake shoe I 04 applies the proper load upon the idling piston to'maintainit in synchronism with the workprevent overheating. It will be understood that if desired the brake shoe I04 may be manually pressed against the brake band,

the like,

In a two cycle engine which is not working maximum speed is limited by of the exhaust conduit, deflector or muiiier 20a to provide the desired area of opening. Or if desired. an adjustable valve 20| as shown in Figure 13 in the conduit 20a is provided on a valve suitably clamped to the conduit carball 208 at the manifold communicates I prefer to have the idling piston crankshaft operate at about 2200 R. P. M. This may be accomplished with a has an area of about 7.065 square inches, equipped with a muffler having an exhaust opening of about .3633 square inch. For drillin a higher speed, such as 2400 to 2500 R. P. M. is preferred, and in such case an exhaust opening of about one half square inch is desirable. The adjustable exhaust valve 20I or the end H5 of the exhaust muiiller thus may be adjusted for varying the maximum ungoverned speed of the idling piston crankshaft. maintained small enough so as to avoid excessive blowing out of the lubricating oil, which would interfere with the proper lubrication of the pistons.

The carburetor II is shown in detail in Figures 4, 10, 11 and 12 and to the inlet manifold I2I by a screw I22. The inlet manifold contains a Venturi or similar restriction I23 with a tube I24 at the throat thereof, and abore I25 extending through boss I26 on therewith and terminates adjacent the bottom of the supply bowl I20. The opening in tube I24may be regulated by a needle valve I21 bore at the opposite side of the manifold. Beyond the Venturi restriction I24 is a second tube I3I threaded into thewall of the manifold and connected to bores I32. I33 and I34 to a'point near the bottom of the bowl. The opening in tube I3I is regulated by a needle valve I36. The flow of air through manifold I2I applies a suction action to tubes I25 and I34 that draws a jet of fuel into the manifold to mix with the air. The bore I34 supplies fuel at idling speed, and the bore I25 supplemented somewhat by bore I34 supplies fuel to the inlet at operating speed.

Fuel is supplied to the inlet bowl I20 through an inlet nozzle I31 connected by a tube I38 to the fuel tank I0, and a valve I40 guided in a tube I4I has a tapered end I42 adaptedto engage a tapered seat I43 to control the fuel supplied to the bowl I20. The valve I40 is governed by an annular float I44 having a connecting arm I45 secured thereto and pivoted on a pivot pin I46, passing through tabs I46 and having a forked end I4! which engages a stem I40 terminating in a head I50. of the lever engages the valve against its seat, and the forked end I41 engages the head I50 to move the valve off its seat, the stem I48 being long enough to allow lost motion. Fuel tank I is closed by a cap I28 designed to allow air to enter the tank to. replace the fuel, but prevent spilling of fuel from the air inletdue to vibration of the apparatus during operation. As shown in Figure 14 a tube I29 is coiled about inside ca'p I28 and has its one end I30 soldered at an air opening the op osite end I301) being free and at the center. This provides a barrier which prevents flow of fuel through the tube I29 and out of opening I30a but allows air to enter.

By having the bores I25 and I34 entering the supply bowl adjacent the bottom and close to the medial vertical axis of the bowl which is inclined i'ith respect to the axis of the motor and by employing an annular float it is possible to operate the apparatus in practically horizontal position as well as in vertical position and still obtain a supply of fuel in the inlet manifold I2I because the annular float remains at all times in contact with the fuel in the bowl to regulate the inlet An extension II However, the exhaust opening is comprises a bowl I20 secured three inch cylinder bore, which acsaoov I valve I40. An air cleaner I55 may be provided on the air inlet pipe I2I, and a butterfly choke valve I56 in the inlet pipe I2I may be adjusted by lever I51 (Fig. 2) to reduce the air supply for starting. The air cleaner I55 and carburetor bowl I20 are protected by a guard plate or housthreaded into a threaded ing I5'Ia suitably held in place and having a hand hole I5Ib therein for access to a bolt I510 which holds the air cleaner I55 in place.

A spring pressed ball detent I58 cooperating with a peripherally notched plate I59 holds the choke valve in full open position as shown in Fig. 11., A throttling valve I6I of the butterfly type is located on stem fuel inlet bore I3I and operating fuel inlet bore I24. This shaft extends through the inlet pipe and has an arm I63 (Fig. 2) suitably fastened thereto. A plate or bracket I65 has inverted channel shaped reinforcing members I66 at each side, and the long stay bolts I61 pass through the flange I68 of tool holder 32, through the flange I69 on the upper end of the crankcase 6, and through plate or bracket I65 and reinforcing channel members I66, and nuts I10 thereon hold the plate I65 in assembled position. The ends HI and I12 of the plate are turned up and a handle bar I13 is welded thereto. The handle I80 provided 'on housing 32 at the bottom together with handle bar I13 provides for carrying or manipulating the apparatus. A hand throttle lever I14 is pivoted at I15 to the handle bar and a push rod I16 passes the handle bar so as to be engaged thereby and be depressed when lever I14 is depressed. A link I11 is pivoted at a bolt I18 in end "I and at one end is fastened, a rod I8I connected to the lever I63 of the throttle valve. The opposite end of link I11 is connected to a rod I82 secured between stop nuts I83 and I84 on the valve plunger rod 58 and a. spring I85 secured to an extension I86 on rod 58 biases the valve rod 58 down. Push rod I16 is secured to.link I11 at I86 so that when the rod is depressed by lever I14 the rod I8I opens the throttle valve while rod I82 is raised, and as rod I32 has a lost motion connection with valve rod 58. valve 56 remains closed until the throttle I48 on the valve I30a in the cap,

valve has been opened. A hand pressure lever I14 is preferred for operating the throttle valve I6I and valve 56 as this is less tiring than one requiring a twist of the wrist to operate. A starting pulley shaft 5 and is enclosed in a housing I9I having a hinged cover held by hasp I92. The apparatus may be started by winding a rope on pulley I90 and giving it a quick tug. meanwhile choking the motor by choke lever I51 as required. In open position the housing I9I falls down as shown in dot and dash lines so as to be out of the way. The apparatus may be stopped by depressing key I93 shown in Fig. 2 to short circuit the magneto.

The operation of the complete apparatus now will be described. Upon rotation of the crankshaft by the cranking wheel or pulley I90 and choking the apparatus by the choke lever I51 as required a mixture of air and fuel is drawn into the crankcase 6 and when the piston 3 moves up toward the crankcase and uncovers port I4'a fuel charge is forced through passage I6 into intake port I4 and into the cylinder 2. As the piston moves down toward the combustion chamber 1 the fuel charge is compressed and is ignitedat about 40 before dead center of crankshaft 5. The explosion resulting therefrom forces piston 9 downwardly until extension 28 strikes the end of tool 3I as previously described and when port I62 between the idlingthrough a suitable hole in I90 is secured to the end of crank- 4B is uncovered the exhaust gas is conducted to the lower chamber 241: and returns the working piston to its upper limit against buffer 33. In the meantime idling piston 8 moves up until its head first uncovers exhaust port l and there uncovers intake I 4 to introduce a fresh fuel charge-into the combustion chamber, the crank returning the idling piston to compress the charge. Should the idling piston operate too rapidly and tend to get out 01' synchronism with the operating piston the brake shoe I 04 is pivoted outwardly by centrifugal force to.engage brake lining I02 and thus automatically apply a load on the crankshaft 5 of idling piston I which reduces its speed. Thus when the fuel supply to the motor is increased the force of the explosion against piston 9 is also increased, but the speed of operation of piston 9 is not greatly increased so that the two pistons exact synchronism is desired the brake may be adjusted manually or automatically.

The supply of fuel to the apparatus is controlled by pressing down pivoted lever H4 to open throttle valve I66 and increase the fuel supplied to the combustion chamber. The connection between throttle valve I66 and valve 56 is such that valve 56 remains closed until throttle valve I 66 has been opened sufliciently to have the idling piston operation at desired speed after which opening of valve 56 causes exhaust gas to be supplied to chamber 24a to cause operation of piston 9.

This application is my application for Internal-combustion operated No. 380,578, filed February 26, 1941, which in turn is a continuation in part of my application Serial No. 360,903, filed October 12, 1940, for Internal combustion operated percussion tool, both now abandoned.

WhatI claim as my invention and desire to secure by United States Letters Patent is:

1. In an internal combustion percussion tool,

combustion chamber, a timing piston reciprocable in said chamber, a second larger chamber connected with the combustion said larger chamber in timed operation of the timing piston.

2. In an internal combustion percussion tool, the combination of a combustion chamber, a timing piston reciprocable in said combustion chamber, a second larger chamber in communication with the portion operating in said combustion chamber and having its larger portion operating in said larger chamber and adapted to impact a tool near the end of its working stroke, a passageway connected to the larger chamber beyond the larger end of the working piston, a port in the combustion chamber connected to the passageway and adapted to be uncovered by the smaller portion of the working piston for controlling the admission of gas from the combustion chamber to the larger cha'mhm- M are maintained very nearly in synchronism. If

a continuation in part of I 12 larger end of the working the working piston.

33. In an internal combustion percussion tool, the combination of a piston controlled by ton when the latter nears the limit of its return stroke and to provide substantially increased rate in the escape of the gases as the working piston approaches said limit.

4. In an internal combustion percussion tool,

continuously open passage to atmosphere providing for intake and exhausting air to and from the larger chamber between the larger and smaller ends of the working piston, said first larger chamber.

larger end oi. the working piston, means responsive to the smaller mm. -s r..- a. a

passageway to beyond the larger end of the working piston whereby to synchronize the working piston with the timing piston, and means re-v connected large and small sections, a differential.

area percussion working piston in said differential cylinder sections having the smaller end operating in the combustion chamber and the larger end operating in the large section, said smaller cylinder section having a port covered by the working piston in its upper position and uncovered in its lower position, said port being connected by a passage to the larger section beyond piston having an extension at the larger end, a

- guide bushing for saidextension, and co-operating escape ports on the extension and guide bushing to provide an exhaust for a substantial time during the initial portion of the working stroke.

7. In an internal combustion percussion tool, the combination of a combustion chamber, a timing piston reciprocable in said chamber to control the combustion of fuel therein, a tool-actuating working piston reciprocable in said chamber and operated by the combustion of fuel therein, and centrifugal brake means arranged to apply a load on the timing piston to control the speed thereof and regulate the frequency of reciprocation of the working piston.

8. In an internal combustion percussion tool,

the combination of a combustion chamber, a timing piston reciprocable in said chamber to control the combustion of fuel therein, atool-actuating working piston reciprocable in said chamber and operated by the combustion of fuel therein, and brake means arranged to apply a load on the timing piston to control the speed thereof and regulate the frequency of reciprocation of the working piston.

9. In an internal combustion percussi'on tool, the combination of a combustion chamber, a timing piston reciprocable in said chamber to control the combustion of fuel therein, a tool-actuating working piston reciprocable in said chamber and driven in working direction by the combustion of fuel in said chamber and returned by exhaust gas, and brake means arranged to apply a load on the timing piston to control the speed thereof and regulate the frequency of reciproca tion of the working piston.

' 10. A percussion tool comprising a casing providing a combustion chamber, a carburetor for supplying fuel to said chamber, a timing piston to control ignition of fuel in said, chamber, a working piston operated by combustion of said fuel, means for employing exhaust gas to cause return movement of the working piston and including a valve, manual means to control the supply of fuel to the combustion chamber, and a lost motion connection between said valve and said manual means to prevent the operation of the working piston until the timing piston is operating at a predetermined speed.

11. In an internal combustion percussion tool, the combination of an internal combustion engine having a timing piston and a percussion working piston operating in predetermined timed relation with respect to one another in a com- 14 bustion'chamber, means to supply and ignite iue in the combustion chamber in timed relation with I the operation of the timing piston to transmit '20 the larger end of the working piston, said working energy to both pistons for producing work, and means independent of normal fuel supply and normal ignition operative, in case the working piston gets out of step with the timing piston as when the former is subjected to a material reduction in load causing a transfer of the energy of combustion to the timing piston and resulting in over-speed, to check the speed of the racing timing piston while combustion subsists to bring the working piston into step with the timing piston to produce work.

12. In an" internal combustion percussion tool, the combination of an internal combustion engine having a timing piston and a percussion working piston operating in predetermined timed relation with respect to one another in a combustion chamber, means to supply and ignite fuel in the combustion chamber in timed relation with the operation of the timing piston to transmit energy to both pistons for producing work, and brake means operative, in case the working piston gets out of step with the timing piston as when the former is subjected to a material reduction in load causing a transfer of the energy of combustion to the timing piston and resultingin over-speed, to check the speed of the racing timing piston while combustion subsists to bring the working piston into step with the timing piston to produce work.

13. In an internal combustion percussion tool, the combination of an,internal combustion engine having a timing piston and a percussion Working piston operating in predetermined timed relation with respect to one another in a combustion chamber, means to supply and ignite fuel in the combustion chamber in timed relation with the operation of the timing piston to transmit energy to both pistons for producing work, and

of step with the timing piston as when the former is subjected to a material reduction in load causing a transfer of the energy of combustion to the timing piston and resulting in over-speed, to check the speed of the racing timing piston while combustion subsists to bring the working piston into step with the timing piston to produce work.

14. In an internal combustion percussion tool, the combination of a casing providing a combustion chamber, a timing piston reciprocable in said chamber, a second larger chamber connected to the combustion chamber, a differential area working piston having its smaller end exposed to and reciprocating in said combustion chamber and having its larger end operating in said larger chamber, a guide stern extending from the larger end ofsaid piston, and a guide bore receiving said stem whereby said working piston is guided by said stem and by the smaller end of the piston, a passage between the combustion chamber and said -large chamber, means responsive to the smaller end of the working piston for controlling the admission of gas from the combustion chamber through said passage to the larger chamber to return the working piston; means to exhaust the gas from the large chamber and the passage during a greater portion of the return stroke of the working piston, and a passage providing for the intake and exhaust of air to the larger chamber between the larger and smaller ends of the workingpiston. a

15. In an internal combustion percussion tool.

15 the combination 01' a casing providing a combustion chamber, a timing piston reciprocable in said chamber, a second larger chamber connected to the combustion chamber, a differential area working piston having one end exposed to said combustion chamber and havingdts larger end operating in said larger chamber, appassageway controlled by the smaller end of the working piston to supply gas under pressure from the combustion chamber to said larger chamber, a valve in said passageway to open or close the same, a throttle arranged to regulate the supply of fuel to the combustion chamber to operate said pistons, and means connecting the throttle with the valve to open the latter when the throttle is actuated.

16. In an internal combustion percussion tool, the combination of a combustion chamber, a timing piston reciprocable in the combustion chamber to control the supply of fuel and its ignition and to control the atmospheric exhaust of products of combustion from the combustion chamber, a. tool-actuating working piston reciprocable in the combustion chamber and driven in a working direction by the combustion of fuel and returned bv exhaust gas, means to regulate the 16 atmospheric exhaust from the combustion chamber to limit the speed of operation of the timing piston, and brake means to apply a load on the timing piston to control the speed thereof below said limit and regulate the frequency of reciprocation of the working piston.

CARL S. WEYANDT.

REFERENCES CITED The following references are of record in the file of this'patent:

UNITED STATES PATENTS Number Name Date 226,539 Neill Apr. 13, 1880 805,633 Clement Nov. 28, 1905 1,308,811 Scott July 8, 1919 1,593,704 Morris July 27, 1926 1,598,476 Cribier Aug. 31, 1926 1,726,599 Wasson Sept. 3, 1929 1,813,513 Saunders July 7, 1931 1,891,411 Greve Dec. 20, 1932 1,920,765 Rasch Aug. 1, 1933 1,981,764 Warsop Nov. 20, 1934 2,029,318 Hagenbook Feb. 4, 1936 2,056,293 Rasch Oct. 6, 1936 

